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  • 2000-2004  (4)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Effects of ozone on photosynthetic CO2 exchange, chlorophyll a fluorescence and antioxidant systems in lettuce leaves (2002)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 116 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of ozone exposure on lettuce leaves were investigated by means of gas exchange, modulated chlorophyll a fluorescence and antioxidants systems. High ozone concentration decreased the rate of photosynthesis at light saturation level and changes in stomatal conductance and transpiration rate. However, an increase in intercellular CO2 concentration indicated a decrease in the carboxylation efficiency. These data agreed with a reduction of non-cyclic electron flow and lower capacity to reduce the quinone pool. Ozone affected the ascorbate pool and decreased ascorbate peroxidase activity, increased lipid peroxidation, altered membrane properties and reduced the development of non-photochemical quenching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1160305.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    In vivo sucrose stimulation of colour change in citrus fruit epicarps: Interactions between nutritional and hormonal signals (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 112 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: During ripening, citrus fruit-peel undergoes ‘colour break’, a process characterized by the conversion of chloroplast to chromoplast. The process involves the progressive loss of chlorophylls and the gain of carotenoids, changing peel colour from green to orange. In the present work, the in vivo and in vitro effects of supplemented nutrients (sucrose and nitrogen) and phytohormones (gibberellins [GA] and ethylene) on colour change in fruit epicarp of Satsuma mandarin (Citrus unshiu (Mak.) Marc., cv. Okitsu), were studied. The rate of colour break was correlated positively with sucrose content and negatively with nitrogen content. The removal of leaves blocked natural sucrose build-up and nitrogen reduction in the peel. Defoliation also inhibited chlorophyll disappearance and carotenoid accumulation, thereby preventing colour break. In vivo sucrose supplementation promoted sucrose accumulation and advanced colour break. In both in vivo and in vitro experiments, colour change promoted by sucrose was unaffected by ethylene but delayed by GA3. In non-supplemented plants, ethylene accelerated colour break while GA3 had no detectable effects. Ethylene inhibitors effectively counteracted the sucrose effects on colour change. Collectively, these results suggest that the chloroplast to chromoplast conversion in citrus fruit epicarps is stimulated by sucrose accumulation. The sugar regulation appears to operate via ethylene, whereas GA may act as a repressor of the sucrose-ethylene stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1120213.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of photosynthesis through source: sink imbalance in citrus is mediated by carbohydrate content in leaves (2002)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 116 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In citrus, the occurrence of a sink effect on photosynthesis (A) is controversial. Leaf carbohydrates and photosynthetic rates in field-grown trees of Satsuma mandarin (Citrus unshiu[Mak.] Marc.) cv. Okitsu, were measured to elucidate whether or not the demand for photoassimilates regulates A. The data indicated that the source-sink imbalances induced by different treatments altered both soluble (sucrose, glucose and fructose) and insoluble carbohydrates in leaves, as well as photosynthetic rates. In general, girdling and defruiting increased starch and reduced photosynthesis, whereas source-limiting conditions imposed through partial defoliations had the opposite effect. These results are compatible with the assumption that a lack of sink activity leads to carbohydrate accumulation and feedback inhibition of A, and vice versa. Further evidence supporting a source-sink effect on A was provided by measurements of the dry matter:leaf area ratio, since defoliations, for example, increased this ratio. The in vivo sucrose supplementation to plants with different source:sink ratios (control, defoliated, girdled and defruited plants) increased carbohydrates and reduced photosynthesis. This suggests that sugars may have, per se, the potential to repress photosynthetic rates in intact plants with active sinks. Based on these results we propose that sugar accumulation in citrus leaves causes a feedback inhibition of A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1160416.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    N-(6-Amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl) derivatives of glycine, valine, serine, threonine and methionine: interplay of molecular, molecular–electronic and supramolecular structures (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 882-892 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: In each of N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)valine, C10H15N5O4 (3) (orthorhombic, P212121), N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)serine monohydrate, C8H11N5O5·H2O (4) (orthorhombic, P212121), and N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl)threonine, C9H13N5O5(5) (monoclinic, P21), the C-nitroso fragments exhibit almost equal C—N and N—O bond lengths: the C—N range is 1.315 (3)–1.329 (3) Å and the N—O range is 1.293 (3)–1.326 (3) Å. In each compound there are also very short intermolecular O—H...O hydrogen bonds, in which carboxyl groups act as hydrogen-bond donors to the nitrosyl O atoms: the O...O distances range from 2.440 (2) to 2.504 (4) Å and the O—H...O angles lie between 161 and 163°. An interpretation of the relationship between the unusual intramolecular bond lengths and the very short intermolecular hydrogen bonds has been developed based on database analysis and computational modelling. In each of (3)–(5) there is an extensive network of intermolecular hydrogen bonds, generating three-dimensional frameworks in (3) and (5), and two-dimensional sheets in (4).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768100005437
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    Paper (German National Licenses)
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